Dunno your gaming resolution, but if its 1920 or higher you'll be happier with a 1GB 460. And even happier if you decide you want/need to go with two. Couldn't quickly find a 2x460 vs 2x5830 benchmark with current drivers, probably because they're faster than 2x5850.
The rest of your choices look very good indeed. I had forgotten the review of that 850W psu.
This is a great power supply, but it's huge overkill for an HD5830. It's more than you need even for 2. If you want to be prepared for a crossfire setup, go with a 750W power supply (plenty for 2 HD5850s as well). Otherwise, you could save a ~$100 with the perfectly capable OCZ ModXStream 600W power supply (Modular, 80 Plus Certified, Generally well reviewed).
Definately don't go with the 5830. I would much sooner drop to an i5 build to get a beter GPU than use the 5830.
At the least go with a GTX460 1gb (if you plan to to use two in future) if only ever going with one GPU then the 5850 is a bettter choice. Course, with GTX 460 at only $200 atm, 2 of them is a great choice.
There is a good deal with the GTX 460 and an 850W Corsair PSU - excessive for your needs in terms of power, but at that price its worth considering and leaves plenty of room if you upgrade stuff in future.